Although a potential demand for high-precision position management by means of wireless tags has hitherto become evident from the standpoint of distribution and security management and the like, a necessary level of measurement precision has not been attained, and therefore such position management has not become widely established.
However, with the development of UWB (Ultra Wide Band) technology in recent years, the trend of opening-up of frequencies has increased the possibility of making possible radio positioning on the order of several cm to several tens of cm.
For example, in Patent Literature 1, a position measurement method (positioning method) is disclosed whereby a position of a node is measured using a radio communication system having a node (corresponding to a wireless tag) provided with a function for transmitting a positioning signal, and a plurality of base stations (corresponding to tag readers). With this positioning method, at least one of a plurality of base stations transmits a reference signal after receiving a positioning signal. Also, at least two of the plurality of base stations measure a time at which a positioning signal is received, and a time at which a reference signal is received. With this positioning system, the position of a node is calculated using reception times of a positioning signal and reference signal measured by a base station having received the reference signal, and position information of a base station having received the positioning signal.
Also, in Non-Patent Literature 1, an implementation example is disclosed in which UWB is applied to the positioning method disclosed in Patent Literature 1.